Exhaust gas emitted from an internal combustion engine is a heterogeneous mixture that contains gaseous emissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”) as well as condensed phase materials (liquids and solids) that constitute particulate matter. Catalyst compositions typically disposed on catalyst supports or substrates are provided in a diesel engine exhaust system to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components.
Particulate filters remove the particulate matter from the exhaust gas. The particulate matter accumulates within the particulate filter. The accumulated particulate matter causes an increase in exhaust system backpressure experienced by the engine. To address this increase, the particulate filter is periodically cleaned, or regenerated. Regeneration of a particulate filter in vehicle applications is typically automatic and is controlled by an engine or other controller based on an estimation of a level of particulate matter in the particulate filter. However, estimations of a level of particulate can be inaccurate, such as when unknown or undetermined conditions occur that may impact (e.g., increase or decrease) levels of particulate matter in the exhaust system.
Accordingly, it is desirable to provide a way to more accurately estimate a level of particulate matter in a particulate filter.